In the field of communication, user equipment has to perform in advance a Physical Random Access Channel (PRACH) procedure due to differences between locations and moving speeds of a plurality of user equipment within a cell, so as to perform uplink communications with a base station. During the PRACH procedure, the user equipment sends a Preamble to the base station on a PRACH channel. Because the base station knows at which position and which time the PRACH channel should appear, the base station can calculate, based on the position and time at which the PRACH channel appears as well as the time when the Preamble sent by the user equipment is actually received on the PRACH channel, a Timing Advance (TA) for the user equipment, and provides to the user equipment the TA in a response message. Afterwards, the user equipment can utilize the TA to perform uplink communications with the base station before a triggering condition which requires obtaining the TA occurs again.
In Release 10 (R10) of an LTE (Long Term Evolution) system (for example, a system 100 as shown in FIG. 1), a base station 101 allocates to a user equipment a Primary Cell (Pcell) 102 that provides services to the user equipment. In some conditions, the base station 101 may further have to allocate one or more of Secondary Cells (Scells) 103a, 103b, and 103c (generally called a Scell 103) to the user equipment. As known to those skilled in the art, in R10, both the cell 102 and cell 103 use the same TA as being located in a same frequency band. Thus, the user equipment needs not performing multiple PRACH procedures in these cells in order to perform uplink communications within respective cells. Generally, it is sufficient to only perform the PRACH procedure once on the Pcell 102, and the obtained TA may be equivalently used by the Scell 103.